The invention relates to a rotary damper for damping a relative rotation of a housing or a rotor by resistance of a viscous fluid, and an assist grip device using the same.
FIG. 6 is a perspective view showing an example of a conventional rotary damper, and FIG. 7 is a sectional view taken along line 7xe2x80x947 in FIG. 6.
In these drawings, D represents a rotary damper. The rotary damper includes a housing 1; a rotor 8 and a main portion 9 which are inserted into an annular chamber 5 of the housing 1; O-shaped rings 12 and 13 as sealing members for sealing between the rotor 8 and the housing 1; and a viscous fluid 15, such as silicone oil, to be filled into a fill space 14 formed by the housing 1, rotor 8 and O-shaped rings 12 and 13.
The housing 1 includes a bottom 2 in an annular ring shape; an outer cylindrical circumferential wall 3 continuously disposed on an outer circumferential edge of the bottom 2; and an inner cylindrical circumferential wall 4 continuously disposed on an inner circumferential edge of the bottom 2.
The outer circumferential wall 3 is provided with an annular step 3a on an inner side of a forward end thereof for receiving therein the O-shaped ring 12; an annular portion 3b on the forward end side of the step 3a; and a protrusion 3c extending in an axial direction on an outer circumference thereof with a predetermined height. The inner circumferential wall 4 includes an annular step 4a for receiving therein the O-shaped ring 13 on an outer side of the forward end thereof.
Incidentally, the circular annular chamber 5 is formed of the bottom 2, the outer circumferential wall 3 and the inner circumferential wall 4. An insertion hole 6 is formed at the center, i.e. inner side, of the inner circumferential wall 4.
The rotor 8 is structured by a rotor main portion 9 to be inserted into the annular chamber 5 of the housing 1; a circular through-hole 10a continuously connected to the rotor main portion 9 and communicating with the insertion hole 6 of the housing 1; and a circular cap portion 10 for closing the annular chamber 5. The cap portion 10 is provided, on an outer circumferential surface thereof, with an annular convex portion 10b to fit the annular portion 3b of the outer circumferential wall 3, and on an outer side surface thereof, with engaging projections 10c extending along a diameter direction.
The rotary damper D, structured as described above, damps relative rotation of the housing 1 and the rotor 8, when the housing 1 and the rotor 8 are relatively rotated, by the viscous and shear resistance of the viscous fluid 15 passing between the outer circumferential wall 3 and the rotor main portion 9 and between the inner circumferential wall 4 and the rotor main portion 9.
Incidentally, the rotary damper D as described above is disclosed in, for example, West Germany Utility Model No. 296 04 260 U1.
The conventional rotary damper D as described above has a simple structure such that the annular convex portion 10b of the cap portion 10 is fit into the annular concave portion 3b of the outer circumferential wall 3 to thereby attach the rotor 8 to the housing 1. Therefore, it is possible to lower a cost of an attaching structure, so that the rotary damper can be provided at a low cost.
However, since the attaching structure between the rotor 8 and the housing 1 is a simple engagement, it is difficult to secure a tight sealing therebetween to prevent the viscous fluid 15 from leaking. When the viscous fluid 15 leaks, an effective damping force can not be obtained.
To prevent the inner fluid leak, the main portion 9 of the rotor 8 and the cap portion 10 can be structured separately so that the rotor can rotate, and then the cap portion 10 is welded to the housing. In this structure, it is possible to secure the sealing and prevent the viscous fluid leak. However, the structure cost for securing the sealing becomes higher, resulting in a higher price of the rotary damper.
The present invention has been made to obviate the above-described disadvantages, and an object of the present invention is to provide a rotary damper, wherein sufficient sealing ability can be obtained and the rotary damper can be produced at a low cost.
Another object of the present invention is to provide an assist grip device using the rotary damper as stated above.
Further objects and advantages of the invention will be apparent from the following description of the invention.
In the present invention, a rotary damper includes a housing having an annular chamber; a rotor with a main body inserted into the annular chamber and a cap portion to close the annular chamber; sealing members for sealing between the rotor and the housing; and a viscous fluid filled in a fill space formed by the housing, rotor and sealing members. More specifically, the rotor is attached to the housing with a structure such that an engaging shoulder portion is provided on one of the housing and the rotor, and an engaging portion is provided on the other thereof. As the engaging portion engages the engaging shoulder portion, the rotor can be securely attached to the housing with tight sealing, and the rotor and the housing can be easily assembled.
It is preferable that an insertion hole is provided at the center of the annular chamber of the housing; an insertion cylinder communicating with the through hole and to be fitted into the insertion hole is provided to the rotor; an engaging portion is provided to the insertion cylinder; an engaging shoulder portion is provided to the housing; and, further, the engaging portion is formed by clamping.
Also, when the rotary damper is used in an assist grip device that is urged to a return position by an urging device, the rotational movement is damped by the rotary damper.